[Cleanup] String::GetChars() should assert against heap allocation

R=jkummerow@chromium.org

Bug: v8:8238
Change-Id: Ie28326ebe6c69e194857aed7b5d49cb8e5a40a29
Reviewed-on: https://chromium-review.googlesource.com/c/1349243Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57821}

src/builtins/builtins-string.cc

@@ -109,6 +109,7 @@ BUILTIN(StringFromCodePoint) {
       isolate->factory()->NewRawTwoByteString(
           static_cast<int>(one_byte_buffer.size() + two_byte_buffer.size())));
 
+  DisallowHeapAllocation no_gc;
   CopyChars(result->GetChars(), one_byte_buffer.data(), one_byte_buffer.size());
   CopyChars(result->GetChars() + one_byte_buffer.size(), two_byte_buffer.data(),
             two_byte_buffer.size());
@@ -467,6 +468,7 @@ V8_WARN_UNUSED_RESULT static Object* ConvertCase(
     String::FlatContent flat_content = s->GetFlatContent();
     DCHECK(flat_content.IsFlat());
     bool has_changed_character = false;
+    DisallowHeapAllocation no_gc;
     int index_to_first_unprocessed = FastAsciiConvert<Converter::kIsToLower>(
         reinterpret_cast<char*>(result->GetChars()),
         reinterpret_cast<const char*>(flat_content.ToOneByteVector().start()),

src/builtins/builtins-trace.cc

@@ -34,6 +34,7 @@ class MaybeUtf8 {
         // Why copy? Well, the trace event mechanism requires null-terminated
         // strings, the bytes we get from SeqOneByteString are not. buf_ is
         // guaranteed to be null terminated.
+        DisallowHeapAllocation no_gc;
         memcpy(buf_, Handle<SeqOneByteString>::cast(string)->GetChars(), len);
       }
     } else {

src/heap/factory.cc

@@ -664,6 +664,7 @@ MaybeHandle<String> Factory::NewStringFromUtf8(Vector<const char> string,
       NewRawTwoByteString(non_ascii_start + utf16_length, pretenure), String);
 
   // Copy ASCII portion.
+  DisallowHeapAllocation no_gc;
   uint16_t* data = result->GetChars();
   for (int i = 0; i < non_ascii_start; i++) {
     *data++ = *ascii_data++;
@@ -677,23 +678,31 @@ MaybeHandle<String> Factory::NewStringFromUtf8(Vector<const char> string,
 MaybeHandle<String> Factory::NewStringFromUtf8SubString(
     Handle<SeqOneByteString> str, int begin, int length,
     PretenureFlag pretenure) {
-  const char* ascii_data =
-      reinterpret_cast<const char*>(str->GetChars() + begin);
-  int non_ascii_start = String::NonAsciiStart(ascii_data, length);
+  Access<UnicodeCache::Utf8Decoder> decoder(
+      isolate()->unicode_cache()->utf8_decoder());
+  int non_ascii_start;
+  int utf16_length = 0;
+  {
+    DisallowHeapAllocation no_gc;
+    const char* ascii_data =
+        reinterpret_cast<const char*>(str->GetChars() + begin);
+    non_ascii_start = String::NonAsciiStart(ascii_data, length);
+    if (non_ascii_start < length) {
+      // Non-ASCII and we need to decode.
+      auto non_ascii = Vector<const char>(ascii_data + non_ascii_start,
+                                          length - non_ascii_start);
+      decoder->Reset(non_ascii);
+
+      utf16_length = static_cast<int>(decoder->Utf16Length());
+    }
+  }
+
   if (non_ascii_start >= length) {
     // If the string is ASCII, we can just make a substring.
     // TODO(v8): the pretenure flag is ignored in this case.
     return NewSubString(str, begin, begin + length);
   }
 
-  // Non-ASCII and we need to decode.
-  auto non_ascii = Vector<const char>(ascii_data + non_ascii_start,
-                                      length - non_ascii_start);
-  Access<UnicodeCache::Utf8Decoder> decoder(
-      isolate()->unicode_cache()->utf8_decoder());
-  decoder->Reset(non_ascii);
-
-  int utf16_length = static_cast<int>(decoder->Utf16Length());
   DCHECK_GT(utf16_length, 0);
 
   // Allocate string.
@@ -704,9 +713,11 @@ MaybeHandle<String> Factory::NewStringFromUtf8SubString(
 
   // Update pointer references, since the original string may have moved after
   // allocation.
-  ascii_data = reinterpret_cast<const char*>(str->GetChars() + begin);
-  non_ascii = Vector<const char>(ascii_data + non_ascii_start,
-                                 length - non_ascii_start);
+  DisallowHeapAllocation no_gc;
+  const char* ascii_data =
+      reinterpret_cast<const char*>(str->GetChars() + begin);
+  auto non_ascii = Vector<const char>(ascii_data + non_ascii_start,
+                                      length - non_ascii_start);
 
   // Copy ASCII portion.
   uint16_t* data = result->GetChars();
@@ -728,12 +739,14 @@ MaybeHandle<String> Factory::NewStringFromTwoByte(const uc16* string,
     Handle<SeqOneByteString> result;
     ASSIGN_RETURN_ON_EXCEPTION(isolate(), result,
                                NewRawOneByteString(length, pretenure), String);
+    DisallowHeapAllocation no_gc;
     CopyChars(result->GetChars(), string, length);
     return result;
   } else {
     Handle<SeqTwoByteString> result;
     ASSIGN_RETURN_ON_EXCEPTION(isolate(), result,
                                NewRawTwoByteString(length, pretenure), String);
+    DisallowHeapAllocation no_gc;
     CopyChars(result->GetChars(), string, length);
     return result;
   }
@@ -828,6 +841,7 @@ Handle<String> Factory::AllocateTwoByteInternalizedString(
   answer->set_length(str.length());
   answer->set_hash_field(hash_field);
   DCHECK_EQ(size, answer->Size());
+  DisallowHeapAllocation no_gc;
 
   // Fill in the characters.
   MemCopy(answer->GetChars(), str.start(), str.length() * kUC16Size);
@@ -861,6 +875,7 @@ Handle<String> Factory::AllocateInternalizedStringImpl(T t, int chars,
   answer->set_length(chars);
   answer->set_hash_field(hash_field);
   DCHECK_EQ(size, answer->Size());
+  DisallowHeapAllocation no_gc;
 
   if (is_one_byte) {
     WriteOneByteData(t, SeqOneByteString::cast(*answer)->GetChars(), chars);
@@ -876,6 +891,7 @@ Handle<String> Factory::NewInternalizedStringFromUtf8(Vector<const char> str,
   if (IsOneByte(str, chars)) {
     Handle<SeqOneByteString> result =
         AllocateRawOneByteInternalizedString(str.length(), hash_field);
+    DisallowHeapAllocation no_allocation;
     MemCopy(result->GetChars(), str.start(), str.length());
     return result;
   }
@@ -886,6 +902,7 @@ Handle<String> Factory::NewOneByteInternalizedString(Vector<const uint8_t> str,
                                                      uint32_t hash_field) {
   Handle<SeqOneByteString> result =
       AllocateRawOneByteInternalizedString(str.length(), hash_field);
+  DisallowHeapAllocation no_allocation;
   MemCopy(result->GetChars(), str.start(), str.length());
   return result;
 }
@@ -895,6 +912,7 @@ Handle<String> Factory::NewOneByteInternalizedSubString(
     uint32_t hash_field) {
   Handle<SeqOneByteString> result =
       AllocateRawOneByteInternalizedString(length, hash_field);
+  DisallowHeapAllocation no_allocation;
   MemCopy(result->GetChars(), string->GetChars() + offset, length);
   return result;
 }
@@ -1052,6 +1070,7 @@ static inline Handle<String> MakeOrFindTwoCharacterString(Isolate* isolate,
                                     1));  // because of this.
     Handle<SeqOneByteString> str =
         isolate->factory()->NewRawOneByteString(2).ToHandleChecked();
+    DisallowHeapAllocation no_allocation;
     uint8_t* dest = str->GetChars();
     dest[0] = static_cast<uint8_t>(c1);
     dest[1] = static_cast<uint8_t>(c2);
@@ -1059,6 +1078,7 @@ static inline Handle<String> MakeOrFindTwoCharacterString(Isolate* isolate,
   } else {
     Handle<SeqTwoByteString> str =
         isolate->factory()->NewRawTwoByteString(2).ToHandleChecked();
+    DisallowHeapAllocation no_allocation;
     uc16* dest = str->GetChars();
     dest[0] = c1;
     dest[1] = c2;
@@ -1188,6 +1208,7 @@ Handle<String> Factory::NewSurrogatePairString(uint16_t lead, uint16_t trail) {
 
   Handle<SeqTwoByteString> str =
       isolate()->factory()->NewRawTwoByteString(2).ToHandleChecked();
+  DisallowHeapAllocation no_allocation;
   uc16* dest = str->GetChars();
   dest[0] = lead;
   dest[1] = trail;
@@ -1221,15 +1242,15 @@ Handle<String> Factory::NewProperSubString(Handle<String> str, int begin,
     if (str->IsOneByteRepresentation()) {
       Handle<SeqOneByteString> result =
           NewRawOneByteString(length).ToHandleChecked();
-      uint8_t* dest = result->GetChars();
       DisallowHeapAllocation no_gc;
+      uint8_t* dest = result->GetChars();
       String::WriteToFlat(*str, dest, begin, end);
       return result;
     } else {
       Handle<SeqTwoByteString> result =
           NewRawTwoByteString(length).ToHandleChecked();
-      uc16* dest = result->GetChars();
       DisallowHeapAllocation no_gc;
+      uc16* dest = result->GetChars();
       String::WriteToFlat(*str, dest, begin, end);
       return result;
     }

src/json-parser.cc

@@ -667,6 +667,7 @@ Handle<Object> JsonParser<seq_one_byte>::ParseJsonNumber() {
   int length = position_ - beg_pos;
   double number;
   if (seq_one_byte) {
+    DisallowHeapAllocation no_gc;
     Vector<const uint8_t> chars(seq_source_->GetChars() + beg_pos, length);
     number = StringToDouble(chars,
                             NO_FLAGS,  // Hex, octal or trailing junk.
@@ -726,9 +727,13 @@ Handle<String> JsonParser<seq_one_byte>::SlowScanJsonString(
   int length = Min(max_length, Max(kInitialSpecialStringLength, 2 * count));
   Handle<StringType> seq_string =
       NewRawString<StringType>(factory(), length, pretenure_);
-  // Copy prefix into seq_str.
-  SinkChar* dest = seq_string->GetChars();
-  String::WriteToFlat(*prefix, dest, start, end);
+
+  {
+    DisallowHeapAllocation no_gc;
+    // Copy prefix into seq_str.
+    SinkChar* dest = seq_string->GetChars();
+    String::WriteToFlat(*prefix, dest, start, end);
+  }
 
   while (c0_ != '"') {
     // Check for control character (0x00-0x1F) or unterminated string (<0).
@@ -879,8 +884,6 @@ Handle<String> JsonParser<seq_one_byte>::ScanJsonString() {
     } else {
       hash = static_cast<uint32_t>(length);
     }
-    Vector<const uint8_t> string_vector(seq_source_->GetChars() + position_,
-                                        length);
     StringTable string_table = isolate()->heap()->string_table();
     uint32_t capacity = string_table->Capacity();
     uint32_t entry = StringTable::FirstProbe(hash, capacity);
@@ -894,12 +897,16 @@ Handle<String> JsonParser<seq_one_byte>::ScanJsonString() {
             factory()->InternalizeOneByteString(seq_source_, position_, length);
         break;
       }
-      if (!element->IsTheHole(isolate()) &&
-          String::cast(element)->IsOneByteEqualTo(string_vector)) {
-        result = Handle<String>(String::cast(element), isolate());
-        DCHECK_EQ(result->Hash(),
-                  (hash << String::kHashShift) >> String::kHashShift);
-        break;
+      if (!element->IsTheHole(isolate())) {
+        DisallowHeapAllocation no_gc;
+        Vector<const uint8_t> string_vector(seq_source_->GetChars() + position_,
+                                            length);
+        if (String::cast(element)->IsOneByteEqualTo(string_vector)) {
+          result = Handle<String>(String::cast(element), isolate());
+          DCHECK_EQ(result->Hash(),
+                    (hash << String::kHashShift) >> String::kHashShift);
+          break;
+        }
       }
       entry = StringTable::NextProbe(entry, count++, capacity);
     }
@@ -929,6 +936,7 @@ Handle<String> JsonParser<seq_one_byte>::ScanJsonString() {
   int length = position_ - beg_pos;
   Handle<String> result =
       factory()->NewRawOneByteString(length, pretenure_).ToHandleChecked();
+  DisallowHeapAllocation no_gc;
   uint8_t* dest = SeqOneByteString::cast(*result)->GetChars();
   String::WriteToFlat(*source_, dest, beg_pos, position_);
 

src/objects.cc

@@ -11382,6 +11382,7 @@ void String::WriteToFlat(String* src,
                          sinkchar* sink,
                          int f,
                          int t) {
+  DisallowHeapAllocation no_gc;
   String* source = src;
   int from = f;
   int to = t;
@@ -12361,6 +12362,7 @@ bool String::IsTwoByteEqualTo(Vector<const uc16> str) {
 }
 
 uint32_t String::ComputeAndSetHash(Isolate* isolate) {
+  DisallowHeapAllocation no_gc;
   // Should only be called if hash code has not yet been computed.
   DCHECK(!HasHashCode());
 
@@ -12386,6 +12388,7 @@ bool String::ComputeArrayIndex(uint32_t* index) {
 
 
 bool String::SlowAsArrayIndex(uint32_t* index) {
+  DisallowHeapAllocation no_gc;
   if (length() <= kMaxCachedArrayIndexLength) {
     Hash();  // force computation of hash code
     uint32_t field = hash_field();
@@ -16751,6 +16754,7 @@ Handle<String> SeqOneByteSubStringKey::AsHandle(Isolate* isolate) {
 
 
 bool SeqOneByteSubStringKey::IsMatch(Object* string) {
+  DisallowHeapAllocation no_gc;
   Vector<const uint8_t> chars(string_->GetChars() + from_, length_);
   return String::cast(string)->IsOneByteEqualTo(chars);
 }

src/objects/string-inl.h

@@ -239,11 +239,13 @@ class SeqOneByteSubStringKey : public StringTableKey {
 #endif
   SeqOneByteSubStringKey(Isolate* isolate, Handle<SeqOneByteString> string,
                          int from, int length)
-      : StringTableKey(StringHasher::HashSequentialString(
-            string->GetChars() + from, length, isolate->heap()->HashSeed())),
-        string_(string),
-        from_(from),
-        length_(length) {
+      : StringTableKey(0), string_(string), from_(from), length_(length) {
+    // We have to set the hash later.
+    DisallowHeapAllocation no_gc;
+    uint32_t hash = StringHasher::HashSequentialString(
+        string->GetChars() + from, length, isolate->heap()->HashSeed());
+    set_hash_field(hash);
+
     DCHECK_LE(0, length_);
     DCHECK_LE(from_ + length_, string_->length());
     DCHECK(string_->IsSeqOneByteString());
@@ -384,6 +386,7 @@ String* String::GetUnderlying() {
 template <class Visitor>
 ConsString* String::VisitFlat(Visitor* visitor, String* string,
                               const int offset) {
+  DisallowHeapAllocation no_gc;
   int slice_offset = offset;
   const int length = string->length();
   DCHECK(offset <= length);
@@ -474,6 +477,7 @@ Address SeqOneByteString::GetCharsAddress() {
 }
 
 uint8_t* SeqOneByteString::GetChars() {
+  DCHECK(!AllowHeapAllocation::IsAllowed());
   return reinterpret_cast<uint8_t*>(GetCharsAddress());
 }
 
@@ -482,6 +486,7 @@ Address SeqTwoByteString::GetCharsAddress() {
 }
 
 uc16* SeqTwoByteString::GetChars() {
+  DCHECK(!AllowHeapAllocation::IsAllowed());
   return reinterpret_cast<uc16*>(FIELD_ADDR(this, kHeaderSize));
 }
 

src/parsing/scanner-character-streams.cc

@@ -257,6 +257,7 @@ class BufferedCharacterStream : public Utf16CharacterStream {
     buffer_start_ = &buffer_[0];
     buffer_cursor_ = buffer_start_;
 
+    DisallowHeapAllocation no_gc;
     Range<uint8_t> range =
         byte_stream_.GetDataAt(position, runtime_call_stats());
     if (range.length() == 0) {
@@ -310,6 +311,7 @@ class UnbufferedCharacterStream : public Utf16CharacterStream {
   bool ReadBlock() final {
     size_t position = pos();
     buffer_pos_ = position;
+    DisallowHeapAllocation no_gc;
     Range<uint16_t> range =
         byte_stream_.GetDataAt(position, runtime_call_stats());
     buffer_start_ = range.start;

src/regexp/regexp-macro-assembler.cc

@@ -154,6 +154,7 @@ int NativeRegExpMacroAssembler::CheckStackGuardState(
     Isolate* isolate, int start_index, bool is_direct_call,
     Address* return_address, Code re_code, String** subject,
     const byte** input_start, const byte** input_end) {
+  AllowHeapAllocation allow_allocation;
   DCHECK(re_code->raw_instruction_start() <= *return_address);
   DCHECK(*return_address <= re_code->raw_instruction_end());
   int return_value = 0;
@@ -249,6 +250,7 @@ NativeRegExpMacroAssembler::Result NativeRegExpMacroAssembler::Match(
   // String is now either Sequential or External
   int char_size_shift = is_one_byte ? 0 : 1;
 
+  DisallowHeapAllocation no_gc;
   const byte* input_start =
       StringCharacterPosition(subject_ptr, start_offset + slice_offset);
   int byte_length = char_length << char_size_shift;
@@ -287,7 +289,10 @@ NativeRegExpMacroAssembler::Result NativeRegExpMacroAssembler::Execute(
 
   if (result == EXCEPTION && !isolate->has_pending_exception()) {
     // We detected a stack overflow (on the backtrack stack) in RegExp code,
-    // but haven't created the exception yet.
+    // but haven't created the exception yet. Additionally, we allow heap
+    // allocation because even though it invalidates {input_start} and
+    // {input_end}, we are about to return anyway.
+    AllowHeapAllocation allow_allocation;
     isolate->StackOverflow();
   }
   return static_cast<Result>(result);

src/runtime/runtime-regexp.cc

@@ -570,6 +570,7 @@ V8_WARN_UNUSED_RESULT static Object* StringReplaceGlobalAtomRegExpWithString(
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, untyped_res, maybe_res);
   Handle<ResultSeqString> result = Handle<ResultSeqString>::cast(untyped_res);
 
+  DisallowHeapAllocation no_gc;
   for (int index : *indices) {
     // Copy non-matched subject content.
     if (subject_pos < index) {
@@ -739,6 +740,7 @@ V8_WARN_UNUSED_RESULT static Object* StringReplaceGlobalRegExpWithEmptyString(
   int prev = 0;
   int position = 0;
 
+  DisallowHeapAllocation no_gc;
   do {
     start = current_match[0];
     end = current_match[1];

src/runtime/runtime-strings.cc

@@ -327,6 +327,7 @@ RUNTIME_FUNCTION(Runtime_StringBuilderConcat) {
     Handle<SeqOneByteString> answer;
     ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
         isolate, answer, isolate->factory()->NewRawOneByteString(length));
+    DisallowHeapAllocation no_gc;
     StringBuilderConcatHelper(*special, answer->GetChars(),
                               FixedArray::cast(array->elements()),
                               array_length);
@@ -335,6 +336,7 @@ RUNTIME_FUNCTION(Runtime_StringBuilderConcat) {
     Handle<SeqTwoByteString> answer;
     ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
         isolate, answer, isolate->factory()->NewRawTwoByteString(length));
+    DisallowHeapAllocation no_gc;
     StringBuilderConcatHelper(*special, answer->GetChars(),
                               FixedArray::cast(array->elements()),
                               array_length);
@@ -552,6 +554,7 @@ RUNTIME_FUNCTION(Runtime_SparseJoinWithSeparator) {
     Handle<SeqOneByteString> result = isolate->factory()
                                           ->NewRawOneByteString(string_length)
                                           .ToHandleChecked();
+    DisallowHeapAllocation no_gc;
     JoinSparseArrayWithSeparator<uint8_t>(
         FixedArray::cast(elements_array->elements()), elements_length,
         array_length, *separator,
@@ -561,6 +564,7 @@ RUNTIME_FUNCTION(Runtime_SparseJoinWithSeparator) {
     Handle<SeqTwoByteString> result = isolate->factory()
                                           ->NewRawTwoByteString(string_length)
                                           .ToHandleChecked();
+    DisallowHeapAllocation no_gc;
     JoinSparseArrayWithSeparator<uc16>(
         FixedArray::cast(elements_array->elements()), elements_length,
         array_length, *separator,

src/uri.cc

@@ -194,6 +194,7 @@ MaybeHandle<String> Uri::Decode(Isolate* isolate, Handle<String> uri,
       isolate, result, isolate->factory()->NewRawTwoByteString(result_length),
       String);
 
+  DisallowHeapAllocation no_gc;
   CopyChars(result->GetChars(), one_byte_buffer.data(), one_byte_buffer.size());
   CopyChars(result->GetChars() + one_byte_buffer.size(), two_byte_buffer.data(),
             two_byte_buffer.size());

src/value-serializer.cc

@@ -1336,6 +1336,7 @@ MaybeHandle<String> ValueDeserializer::ReadTwoByteString() {
 
   // Copy the bytes directly into the new string.
   // Warning: this uses host endianness.
+  DisallowHeapAllocation no_gc;
   memcpy(string->GetChars(), bytes.begin(), bytes.length());
   return string;
 }

test/cctest/test-code-stub-assembler.cc

@@ -1787,6 +1787,7 @@ TEST(OneToTwoByteStringCopy) {
       isolate->factory()->NewStringFromTwoByte(str).ToHandleChecked();
   FunctionTester ft(asm_tester.GenerateCode(), kNumParams);
   ft.Call(string1, string2);
+  DisallowHeapAllocation no_gc;
   CHECK_EQ(Handle<SeqOneByteString>::cast(string1)->GetChars()[0],
            Handle<SeqTwoByteString>::cast(string2)->GetChars()[0]);
   CHECK_EQ(Handle<SeqOneByteString>::cast(string1)->GetChars()[1],
@@ -1818,6 +1819,7 @@ TEST(OneToOneByteStringCopy) {
       isolate->factory()->NewStringFromOneByte(str).ToHandleChecked();
   FunctionTester ft(asm_tester.GenerateCode(), kNumParams);
   ft.Call(string1, string2);
+  DisallowHeapAllocation no_gc;
   CHECK_EQ(Handle<SeqOneByteString>::cast(string1)->GetChars()[0],
            Handle<SeqOneByteString>::cast(string2)->GetChars()[0]);
   CHECK_EQ(Handle<SeqOneByteString>::cast(string1)->GetChars()[1],
@@ -1849,6 +1851,7 @@ TEST(OneToOneByteStringCopyNonZeroStart) {
       isolate->factory()->NewStringFromOneByte(str).ToHandleChecked();
   FunctionTester ft(asm_tester.GenerateCode(), kNumParams);
   ft.Call(string1, string2);
+  DisallowHeapAllocation no_gc;
   CHECK_EQ(Handle<SeqOneByteString>::cast(string1)->GetChars()[0],
            Handle<SeqOneByteString>::cast(string2)->GetChars()[3]);
   CHECK_EQ(Handle<SeqOneByteString>::cast(string1)->GetChars()[1],
@@ -1880,6 +1883,7 @@ TEST(TwoToTwoByteStringCopy) {
       isolate->factory()->NewStringFromTwoByte(str2).ToHandleChecked();
   FunctionTester ft(asm_tester.GenerateCode(), kNumParams);
   ft.Call(string1, string2);
+  DisallowHeapAllocation no_gc;
   CHECK_EQ(Handle<SeqTwoByteString>::cast(string1)->GetChars()[0],
            Handle<SeqTwoByteString>::cast(string2)->GetChars()[0]);
   CHECK_EQ(Handle<SeqTwoByteString>::cast(string1)->GetChars()[1],

test/cctest/test-strings.cc

@@ -1819,6 +1819,7 @@ TEST(Regress876759) {
   {
     Handle<SeqTwoByteString> raw =
         factory->NewRawTwoByteString(kLength).ToHandleChecked();
+    DisallowHeapAllocation no_gc;
     CopyChars(raw->GetChars(), two_byte_buf, kLength);
     parent = raw;
   }